Even there are sometips how to fix this issue, none of them worked for my case. After all unit tests were removed and one by one added back manualy, I was able to locate the tests causing it. Problematic appeared to be async unit tests and the random factor appeared to be cpu usage. In other words when flashplayer was not able to execute and finish async test, it failed with maven exception. Finally, the day was saved with changed testTimeout value: